Set up global redirects for old versioned docs

Google points to some old documentation page for some phrases, and since we no longer provide these docs, some users may end up with 404. For example, "arcadedb-haystack" points to https://docs.haystack.deepset.ai/reference/2.18/integrations-arcadedb.

Solution: set up some global redirects for older version. Not sure if we should serve the oldest version available, or the current docs.